Because degradation is dependent upon solar radiation, all UV degradation ceases when exposure to UV radiation is terminated. Thus, buried pipelines will not continue to degrade. In fact, any opaque shield, no matter how thin, will effectively prevent UV degradation. The most common method used to protect above ground PVC pipe from the sun is painting with an acrylic or latex (water-based) paint. Preparation of the surface to be painted is very important. The pipe should be cleaned to remove moisture, dirt, and oil, and then wiped with a clean, dry cloth. Petroleum-based paints should not be used since the presence of petroleum will prevent proper bonding of paint to pipe. In addition, PVC pipes intended for outdoor use (e.g. PVC above-ground irrigation pipe) may be formulated with special additives, similar to those used in PVC house siding, that effectively prevent any significant UV degradation.